"""Temporary files.

This module provides generic, low- and high-level interfaces for
creating temporary files and directories.  All of the interfaces
provided by this module can be used without fear of race conditions
except for 'mktemp'.  'mktemp' is subject to race conditions and
should not be used; it is provided for backward compatibility only.

This module also provides some data items to the user:

  TMP_MAX  - maximum number of names that will be tried before
             giving up.
  template - the default prefix for all temporary names.
             You may change this to control the default prefix.
  tempdir  - If this is set to a string before the first use of
             any routine from this module, it will be considered as
             another candidate location to store temporary files.
"""

__all__ = [
  "NamedTemporaryFile", "TemporaryFile",  # high level safe interfaces
  "SpooledTemporaryFile",
  "mkstemp", "mkdtemp",  # low level safe interfaces
  "mktemp",  # deprecated unsafe interface
  "TMP_MAX", "gettempprefix",  # constants
  "tempdir", "gettempdir"
]

# Imports.

import errno as _errno
import io as _io
import os as _os
from random import Random as _Random

try:
  from cStringIO import StringIO as _StringIO
except ImportError:
  from StringIO import StringIO as _StringIO

try:
  import fcntl as _fcntl
except ImportError:
  def _set_cloexec(fd):
    pass
else:
  def _set_cloexec(fd):
    try:
      flags = _fcntl.fcntl(fd, _fcntl.F_GETFD, 0)
    except IOError:
      pass
    else:
      # flags read successfully, modify
      flags |= _fcntl.FD_CLOEXEC
      _fcntl.fcntl(fd, _fcntl.F_SETFD, flags)

try:
  import thread as _thread
except ImportError:
  import dummy_thread as _thread
_allocate_lock = _thread.allocate_lock

_text_openflags = _os.O_RDWR | _os.O_CREAT | _os.O_EXCL
if hasattr(_os, 'O_NOINHERIT'):
  _text_openflags |= _os.O_NOINHERIT
if hasattr(_os, 'O_NOFOLLOW'):
  _text_openflags |= _os.O_NOFOLLOW

_bin_openflags = _text_openflags
if hasattr(_os, 'O_BINARY'):
  _bin_openflags |= _os.O_BINARY

if hasattr(_os, 'TMP_MAX'):
  TMP_MAX = _os.TMP_MAX
else:
  TMP_MAX = 10000

template = "tmp"

# Internal routines.

_once_lock = _allocate_lock()

if hasattr(_os, "lstat"):
  _stat = _os.lstat
elif hasattr(_os, "stat"):
  _stat = _os.stat
else:
  # Fallback.  All we need is something that raises os.error if the
  # file doesn't exist.
  def _stat(fn):
    try:
      f = open(fn)
    except IOError:
      raise _os.error
    f.close()


def _exists(fn):
  try:
    _stat(fn)
  except _os.error:
    return False
  else:
    return True


class _RandomNameSequence:
  """An instance of _RandomNameSequence generates an endless
  sequence of unpredictable strings which can safely be incorporated
  into file names.  Each string is six characters long.  Multiple
  threads can safely use the same instance at the same time.

  _RandomNameSequence is an iterator."""

  characters = ("abcdefghijklmnopqrstuvwxyz" +
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
                "0123456789_")

  def __init__(self):
    self.mutex = _allocate_lock()
    self.normcase = _os.path.normcase

  @property
  def rng(self):
    cur_pid = _os.getpid()
    if cur_pid != getattr(self, '_rng_pid', None):
      self._rng = _Random()
      self._rng_pid = cur_pid
    return self._rng

  def __iter__(self):
    return self

  def next(self):
    m = self.mutex
    c = self.characters
    choose = self.rng.choice

    m.acquire()
    try:
      letters = [choose(c) for dummy in "123456"]
    finally:
      m.release()

    return self.normcase(''.join(letters))


def _candidate_tempdir_list():
  """Generate a list of candidate temporary directories which
  _get_default_tempdir will try."""

  dirlist = []

  # First, try the environment.
  for envname in 'TMPDIR', 'TEMP', 'TMP':
    dirname = _os.getenv(envname)
    if dirname: dirlist.append(dirname)

  # Failing that, try OS-specific locations.
  if _os.name == 'riscos':
    dirname = _os.getenv('Wimp$ScrapDir')
    if dirname: dirlist.append(dirname)
  elif _os.name == 'nt':
    dirlist.extend([r'c:\temp', r'c:\tmp', r'\temp', r'\tmp'])
  else:
    dirlist.extend(['/tmp', '/var/tmp', '/usr/tmp'])

  # As a last resort, the current directory.
  try:
    dirlist.append(_os.getcwd())
  except (AttributeError, _os.error):
    dirlist.append(_os.curdir)

  return dirlist


def _get_default_tempdir():
  """Calculate the default directory to use for temporary files.
  This routine should be called exactly once.

  We determine whether or not a candidate temp dir is usable by
  trying to create and write to a file in that directory.  If this
  is successful, the test file is deleted.  To prevent denial of
  service, the name of the test file must be randomized."""

  namer = _RandomNameSequence()
  dirlist = _candidate_tempdir_list()
  flags = _text_openflags

  for dir in dirlist:
    if dir != _os.curdir:
      dir = _os.path.normcase(_os.path.abspath(dir))
    # Try only a few names per directory.
    for seq in xrange(100):
      name = namer.next()
      filename = _os.path.join(dir, name)
      try:
        fd = _os.open(filename, flags, 0o600)
        try:
          try:
            with _io.open(fd, 'wb', closefd=False) as fp:
              fp.write(b'blat')
          finally:
            _os.close(fd)
        finally:
          _os.unlink(filename)
        return dir
      except (OSError, IOError) as e:
        if e.args[0] == _errno.EEXIST:
          continue
        if (_os.name == 'nt' and e.args[0] == _errno.EACCES and
              _os.path.isdir(dir) and _os.access(dir, _os.W_OK)):
          # On windows, when a directory with the chosen name already
          # exists, EACCES error code is returned instead of EEXIST.
          continue
        break  # no point trying more names in this directory
  raise IOError, (_errno.ENOENT,
                  ("No usable temporary directory found in %s" % dirlist))


_name_sequence = None


def _get_candidate_names():
  """Common setup sequence for all user-callable interfaces."""

  global _name_sequence
  if _name_sequence is None:
    _once_lock.acquire()
    try:
      if _name_sequence is None:
        _name_sequence = _RandomNameSequence()
    finally:
      _once_lock.release()
  return _name_sequence


def _mkstemp_inner(dir, pre, suf, flags):
  """Code common to mkstemp, TemporaryFile, and NamedTemporaryFile."""

  names = _get_candidate_names()

  for seq in xrange(TMP_MAX):
    name = names.next()
    file = _os.path.join(dir, pre + name + suf)
    try:
      fd = _os.open(file, flags, 0600)
      _set_cloexec(fd)
      return (fd, _os.path.abspath(file))
    except OSError, e:
      if e.errno == _errno.EEXIST:
        continue  # try again
      if (_os.name == 'nt' and e.errno == _errno.EACCES and
            _os.path.isdir(dir) and _os.access(dir, _os.W_OK)):
        # On windows, when a directory with the chosen name already
        # exists, EACCES error code is returned instead of EEXIST.
        continue
      raise

  raise IOError, (_errno.EEXIST, "No usable temporary file name found")


# User visible interfaces.

def gettempprefix():
  """Accessor for tempdir.template."""
  return template


tempdir = None


def gettempdir():
  """Accessor for tempfile.tempdir."""
  global tempdir
  if tempdir is None:
    _once_lock.acquire()
    try:
      if tempdir is None:
        tempdir = _get_default_tempdir()
    finally:
      _once_lock.release()
  return tempdir


def mkstemp(suffix="", prefix=template, dir=None, text=False):
  """User-callable function to create and return a unique temporary
  file.  The return value is a pair (fd, name) where fd is the
  file descriptor returned by os.open, and name is the filename.

  If 'suffix' is specified, the file name will end with that suffix,
  otherwise there will be no suffix.

  If 'prefix' is specified, the file name will begin with that prefix,
  otherwise a default prefix is used.

  If 'dir' is specified, the file will be created in that directory,
  otherwise a default directory is used.

  If 'text' is specified and true, the file is opened in text
  mode.  Else (the default) the file is opened in binary mode.  On
  some operating systems, this makes no difference.

  The file is readable and writable only by the creating user ID.
  If the operating system uses permission bits to indicate whether a
  file is executable, the file is executable by no one. The file
  descriptor is not inherited by children of this process.

  Caller is responsible for deleting the file when done with it.
  """

  if dir is None:
    dir = gettempdir()

  if text:
    flags = _text_openflags
  else:
    flags = _bin_openflags

  return _mkstemp_inner(dir, prefix, suffix, flags)


def mkdtemp(suffix="", prefix=template, dir=None):
  """User-callable function to create and return a unique temporary
  directory.  The return value is the pathname of the directory.

  Arguments are as for mkstemp, except that the 'text' argument is
  not accepted.

  The directory is readable, writable, and searchable only by the
  creating user.

  Caller is responsible for deleting the directory when done with it.
  """

  if dir is None:
    dir = gettempdir()

  names = _get_candidate_names()

  for seq in xrange(TMP_MAX):
    name = names.next()
    file = _os.path.join(dir, prefix + name + suffix)
    try:
      _os.mkdir(file, 0700)
      return file
    except OSError, e:
      if e.errno == _errno.EEXIST:
        continue  # try again
      if (_os.name == 'nt' and e.errno == _errno.EACCES and
            _os.path.isdir(dir) and _os.access(dir, _os.W_OK)):
        # On windows, when a directory with the chosen name already
        # exists, EACCES error code is returned instead of EEXIST.
        continue
      raise

  raise IOError, (_errno.EEXIST, "No usable temporary directory name found")


def mktemp(suffix="", prefix=template, dir=None):
  """User-callable function to return a unique temporary file name.  The
  file is not created.

  Arguments are as for mkstemp, except that the 'text' argument is
  not accepted.

  This function is unsafe and should not be used.  The file name
  refers to a file that did not exist at some point, but by the time
  you get around to creating it, someone else may have beaten you to
  the punch.
  """

  ##    from warnings import warn as _warn
  ##    _warn("mktemp is a potential security risk to your program",
  ##          RuntimeWarning, stacklevel=2)

  if dir is None:
    dir = gettempdir()

  names = _get_candidate_names()
  for seq in xrange(TMP_MAX):
    name = names.next()
    file = _os.path.join(dir, prefix + name + suffix)
    if not _exists(file):
      return file

  raise IOError, (_errno.EEXIST, "No usable temporary filename found")


class _TemporaryFileWrapper:
  """Temporary file wrapper

  This class provides a wrapper around files opened for
  temporary use.  In particular, it seeks to automatically
  remove the file when it is no longer needed.
  """

  def __init__(self, file, name, delete=True):
    self.file = file
    self.name = name
    self.close_called = False
    self.delete = delete

  def __getattr__(self, name):
    # Attribute lookups are delegated to the underlying file
    # and cached for non-numeric results
    # (i.e. methods are cached, closed and friends are not)
    file = self.__dict__['file']
    a = getattr(file, name)
    if not issubclass(type(a), type(0)):
      setattr(self, name, a)
    return a

  # The underlying __enter__ method returns the wrong object
  # (self.file) so override it to return the wrapper
  def __enter__(self):
    self.file.__enter__()
    return self

  # NT provides delete-on-close as a primitive, so we don't need
  # the wrapper to do anything special.  We still use it so that
  # file.name is useful (i.e. not "(fdopen)") with NamedTemporaryFile.
  if _os.name != 'nt':
    # Cache the unlinker so we don't get spurious errors at
    # shutdown when the module-level "os" is None'd out.  Note
    # that this must be referenced as self.unlink, because the
    # name TemporaryFileWrapper may also get None'd out before
    # __del__ is called.
    unlink = _os.unlink

    def close(self):
      if not self.close_called:
        self.close_called = True
        try:
          self.file.close()
        finally:
          if self.delete:
            self.unlink(self.name)

    def __del__(self):
      self.close()

    # Need to trap __exit__ as well to ensure the file gets
    # deleted when used in a with statement
    def __exit__(self, exc, value, tb):
      result = self.file.__exit__(exc, value, tb)
      self.close()
      return result
  else:
    def __exit__(self, exc, value, tb):
      self.file.__exit__(exc, value, tb)


def NamedTemporaryFile(mode='w+b', bufsize=-1, suffix="",
                       prefix=template, dir=None, delete=True):
  """Create and return a temporary file.
  Arguments:
  'prefix', 'suffix', 'dir' -- as for mkstemp.
  'mode' -- the mode argument to os.fdopen (default "w+b").
  'bufsize' -- the buffer size argument to os.fdopen (default -1).
  'delete' -- whether the file is deleted on close (default True).
  The file is created as mkstemp() would do it.

  Returns an object with a file-like interface; the name of the file
  is accessible as its 'name' attribute.  The file will be automatically
  deleted when it is closed unless the 'delete' argument is set to False.
  """

  if dir is None:
    dir = gettempdir()

  if 'b' in mode:
    flags = _bin_openflags
  else:
    flags = _text_openflags

  # Setting O_TEMPORARY in the flags causes the OS to delete
  # the file when it is closed.  This is only supported by Windows.
  if _os.name == 'nt' and delete:
    flags |= _os.O_TEMPORARY

  (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
  try:
    file = _os.fdopen(fd, mode, bufsize)
    return _TemporaryFileWrapper(file, name, delete)
  except BaseException:
    _os.unlink(name)
    _os.close(fd)
    raise


if _os.name != 'posix' or _os.sys.platform == 'cygwin':
  # On non-POSIX and Cygwin systems, assume that we cannot unlink a file
  # while it is open.
  TemporaryFile = NamedTemporaryFile

else:
  def TemporaryFile(mode='w+b', bufsize=-1, suffix="",
                    prefix=template, dir=None):
    """Create and return a temporary file.
    Arguments:
    'prefix', 'suffix', 'dir' -- as for mkstemp.
    'mode' -- the mode argument to os.fdopen (default "w+b").
    'bufsize' -- the buffer size argument to os.fdopen (default -1).
    The file is created as mkstemp() would do it.

    Returns an object with a file-like interface.  The file has no
    name, and will cease to exist when it is closed.
    """

    if dir is None:
      dir = gettempdir()

    if 'b' in mode:
      flags = _bin_openflags
    else:
      flags = _text_openflags

    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
    try:
      _os.unlink(name)
      return _os.fdopen(fd, mode, bufsize)
    except:
      _os.close(fd)
      raise


class SpooledTemporaryFile:
  """Temporary file wrapper, specialized to switch from
  StringIO to a real file when it exceeds a certain size or
  when a fileno is needed.
  """
  _rolled = False

  def __init__(self, max_size=0, mode='w+b', bufsize=-1,
               suffix="", prefix=template, dir=None):
    self._file = _StringIO()
    self._max_size = max_size
    self._rolled = False
    self._TemporaryFileArgs = (mode, bufsize, suffix, prefix, dir)

  def _check(self, file):
    if self._rolled: return
    max_size = self._max_size
    if max_size and file.tell() > max_size:
      self.rollover()

  def rollover(self):
    if self._rolled: return
    file = self._file
    newfile = self._file = TemporaryFile(*self._TemporaryFileArgs)
    del self._TemporaryFileArgs

    newfile.write(file.getvalue())
    newfile.seek(file.tell(), 0)

    self._rolled = True

  # The method caching trick from NamedTemporaryFile
  # won't work here, because _file may change from a
  # _StringIO instance to a real file. So we list
  # all the methods directly.

  # Context management protocol
  def __enter__(self):
    if self._file.closed:
      raise ValueError("Cannot enter context with closed file")
    return self

  def __exit__(self, exc, value, tb):
    self._file.close()

  # file protocol
  def __iter__(self):
    return self._file.__iter__()

  def close(self):
    self._file.close()

  @property
  def closed(self):
    return self._file.closed

  def fileno(self):
    self.rollover()
    return self._file.fileno()

  def flush(self):
    self._file.flush()

  def isatty(self):
    return self._file.isatty()

  @property
  def mode(self):
    try:
      return self._file.mode
    except AttributeError:
      return self._TemporaryFileArgs[0]

  @property
  def name(self):
    try:
      return self._file.name
    except AttributeError:
      return None

  def next(self):
    return self._file.next

  def read(self, *args):
    return self._file.read(*args)

  def readline(self, *args):
    return self._file.readline(*args)

  def readlines(self, *args):
    return self._file.readlines(*args)

  def seek(self, *args):
    self._file.seek(*args)

  @property
  def softspace(self):
    return self._file.softspace

  def tell(self):
    return self._file.tell()

  def truncate(self):
    self._file.truncate()

  def write(self, s):
    file = self._file
    rv = file.write(s)
    self._check(file)
    return rv

  def writelines(self, iterable):
    file = self._file
    rv = file.writelines(iterable)
    self._check(file)
    return rv

  def xreadlines(self, *args):
    if hasattr(self._file, 'xreadlines'):  # real file
      return iter(self._file)
    else:  # StringIO()
      return iter(self._file.readlines(*args))
